I know this might be a very simple and easy thing to do, but I have some doubts on how to detect an IR beacon signal, the signal will be detected using a TSOP1738, and its composed by an 40Khz square wave modulated at 600Hz, with a 30% duty-cycle, here is an image that makes it easier to be understood:

I know that my TSOP is a 38Khz model, but as far as I know they also detect signals above and bellow their designated frequency of operation, so I hope it will work.

My doubt is how to detect this signal, use pulse-in?Or interrupts?Or something else?

pulseIn() should work fine and return a number about 1700 (microseconds) for your waveform. The TSOP1738 will convert the 40kHz (hopefully...as you say it's pretty close to 38 kHz) to a steady logic 0 signal. When the 40 kHz light goes away the TSOP1738 will give a steady logic 1 signal.

This is for a micromouse contest, all the other teams use whelled robots, we will try our luck with a Bioloid humanoid, driven by an IGEPv2 board running openCv, so I will ask access to the test track and test the TSOP with pulsein.

We are not in the competition to win, but to showcase what can be done, and to learn a lot.Our micro-mouse contest is not near as fast as those Japanese ones, and our bots have a max size of 40x40cm, so they are big and slow machines, but yes, our humanoid will never in its lifetime do the 7.5mx7.5m labyrinth in the 4min time limit..